Beams, trusses, joists, and columns are the typical structural members that support the weight or loads of structures, including buildings and bridges. Structural members may be manufactured from a variety of materials, including steel, concrete, and wood, according to the structure design, environment, and cost.
Wood structural members are now typically manufactured from multiple wood segments that are bonded together, such as in glue-laminated members, laminated veneer lumber, parallel strand lumber and I-beams. These manufactured wood structural members have replaced sawn lumber or timbers because the former have higher design limits resulting from better inspection and manufacturing controls. Wood is a desireable material for use in many structural members because of its various characteristics, including strength for a given weight, appearance, cyclic load response, and fire resistance.
In any application, a load subjects a structural member to both compressive and tensile stresses, which correspond to the respective compacting and elongating forces induced by the load on opposite sides of the member. By convention, a neutral plane or axis extends between the portions of the member under compression and tension. The structural member must be capable of bearing the compressive and tensile stresses without excessive strain and particularly without ultimately failing.
Reinforcement of wood structural members in regions subjected to tensile stresses are known. For example, U.S. Pat. No. 5,026,593 of O'Brien describes the use of a thin flat aluminum strip to reinforce a laminated beam. The use of a synthetic tension reinforcement having multiple aramid fiber strands held within a resin matrix adhered to at least one of the wood segments in the tension portion of the structural member is described by the inventor of the present application in "Reinforced Glued-Laminated Wood Beams" presented at the 1988 International Conference on Timber Engineering.
Despite prior descriptions of reinforced wood structural members, methods suitable for large scale manufacturing of structural wood members with synthetic reinforcement are not available. Some conventional methods of manufacturing structural wood members are unworkable with synthetic fiber reinforcements. Other conventional methods of manufacturing structural wood members would be inefficient and wasteful of relatively expensive synthetic fiber reinforcement.